A hundred and fifty years ago, Alfred Russel Wallace must have stood in similar awe when he first saw this spectacular birdwing butterfly in Sarawak, a few hundred miles down the coast from where we were hiking. Having arrived in Borneo in November 1854, the naturalist struck up a friendship with the legendary Sir James Brooke, the first “white rajah” of Sarawak. It was Brooke who gave him a specimen of the as-yet-unnamed species. Wallace immediately dispatched a note to the Entomological Society of London, naming the species Ornithoptera brookiana after his new friend, “whose benevolent government of the country in which it was discovered every true Englishman must admire.”

It is tempting to see the note as an early sign of Wallace’s ability to marry science with social issues and with loyalty to a person or a cause, traits that were to both drive and plague him in his later career. But when the thirty-one-year-old Wallace, as the guest of Brooke, was amusing those at the rajah’s dinner table with “his clever and inexhaustible flow of talk—really good talk,” as one dinner guest recalls—his career was just beginning.

Born to a middle-class family of scant means, the young Wallace worked in England and Wales as a land surveyor and schoolteacher, all the while educating himself as a naturalist. At the age of twenty-five, he embarked on the life of a traveling collector, living off the sale of his specimens to museums and private collectors in the British Isles. His travels took him first to South America, where he spent four years traversing the Amazon basin. But he lost most of the collection he amassed there when the vessel carrying him back to England sank in the middle of the Atlantic. Undaunted, he spent the next eighteen months mustering the courage and funds for another trip, this time to the Malay Archipelago, where he would spend eight years before finally settling down in his native country.

Traveling naturalists were not uncommon in the nineteenth century, and Wallace probably would have remained relatively obscure had he not had two world-shattering insights during his stay in Southeast Asia. The first came to him around the same time he penned his description of the Rajah Brooke birdwing. It was the height of the monsoon season, and the incessant rains gave Wallace, who was sojourning in Brooke’s riverfront villa, little else to do but “ponder over the problem which was rarely absent from my thoughts.” Evolution—though not yet called by that name—was a hot topic in the mid-nineteenth century. Nobody, however, had a clear idea of what it was or how it might work—nobody, that is, except Charles Darwin, who for ten years had shared his thoughts with only a few friends.

In Brooke’s villa, Wallace wrote the treatise now known as the “Sarawak Law.” In it he deduces, from the geographic distributions of animals and plants, that ancestor species whose ranges were physically separated split over time into multiple descendant species, a process that biologists today call allopatric speciation. The paper, published in 1855, drew the attention of the leading English geologist of the day, Charles Lyell. Lyell warned his friend Darwin that Wallace seemed on the verge of scooping him. And that, in fact, is what almost happened. Laid up on the island of Ternate in 1858 with a bout of malarial fever, Wallace, in a flash of inspiration, discovered natural selection. When he recuperated, he spent three evenings writing “On the Tendency of Varieties to Depart Indefinitely from the Original Type,” and quickly sent the manuscript off to Darwin for comments.

Then unfolded one of the best-known episodes in the history of science. Realizing that Wallace, in his hut in the Orient, had independently stumbled upon natural selection, Darwin was thrown into a fit of panic and depression. To Lyell he wrote, “Your words have come true with a vengeance. . . . All my originality will be smashed.” Lyell and the botanist Joseph Dalton Hooker helped save the day by arranging for Wallace’s “Ternate essay” and abstracts of Darwin’s still-unpublished treatises to be read jointly at the July 1, 1858, meeting of the Linnaean Society. The rest is history.

Or is it? Wallace is well known today, not only for independently describing natural selection, but also for writing The Malay Archipelago and discovering what has come to be known as Wallace’s Line, the faunal divide that runs between eastern and western Southeast Asia. Few, however, will know that, though he never returned to the Tropics after going home to England in 1862, Wallace’s mind continued to cross boundaries in the second half of his life. His intellectual wanderlust took him, for the most part, away from the field of his early successes and into theism, spiritualism, phrenology, mesmerism, socialism, land nationalization, environmentalism, antivaccinationism, and geocentrism. In truth, he became something of a Victorian cult figure. Most Wallace biographers have ignored, avoided, or derided this latter Wallace, to focus instead on the youthful genius. Now the authors of two new biographies, Ross A. Slotten and Martin Fichman, have sought to correct the bias in an attempt to see the man as a whole.

Slotten’s The Heretic in Darwin’s Court is the more conventional of the two. A physician from Chicago and a Wallace enthusiast, Slotten has produced an admirable biography that conveys sympathy for its misunderstood hero. That sympathy, Slotten’s predilection for quirky details, and his talent for imaginative investigation often make Wallace and his world spring to life.

In 1866, for instance, Wallace had just published The Scientific Aspect of the Supernatural, his first work on spiritualism, and a bundle of copies sat wrapped and bound on his sister Fanny’s table. One morning the bundle was inexplicably scattered about, and Fanny (an ardent spiritualist herself) consulted a Ouija board about the cause of the disruption. The “spirit” guiding Fanny’s hand on the Ouija board urged her to distribute the booklets as quickly as possible, then wrote Fanny’s name in one of them while she held it closed under her hand. Slotten is not content to take the episode on indirect authority. He describes how his research takes him to the archives of the Oxford University Museum of Natural History, where he finds that very copy of Wallace’s book, with the “spirit writing” in red crayon still plainly visible inside it.

Wallace’s fascination with spiritualism also plays an important role elsewhere in Slotten’s book. Not only incidental manifestations of spirits, but especially formal séances made a deep impression on Wallace. An interest in such matters was not as strange as it may seem today. Spirits were all the rage in mid-Victorian London, and organizing or attending séances was a favorite pastime among the higher echelons of society, right up to Queen Victoria herself. The proceedings were normally held in darkened rooms, where tables might float through space, and musical instruments might be played by invisible hands (sometimes, as Wallace wrote in The Scientific Aspect of the Supernatural, “in so wretched a style that the company begged that it might be discontinued”).

But in what Slotten calls a “fatal attraction,” Wallace began his own investigations into the supernatural in 1865. He became a dedicated supporter of several mediums, and urged his fellow scientists to take spiritualist claims seriously, most famously when he chaired a biology section of the annual meeting of the British Association for the Advancement of Science, and used (many said abused) his position to secure the presentation of a paper on spiritualism. Meanwhile, other members of the scientific community in London were doing their best to expose the same mediums as frauds. Darwin’s son George organized a séance at the home of Charles’s brother Erasmus, and urged Charles Darwin’s intellectual “bulldog,” the anatomist and biologist T.H. Huxley, to attend and help detect the “jugglery” of the medium. And at another séance, the zoologist E. Ray Lankester caught the medium Henry Slade in the act of scribbling his own “spirit writings,” which led to the infamous Slade trial. (Wallace testified as a witness for the defense at the trial, while Darwin discreetly offered to foot part of the bill for the prosecution.)

Wallace’s precarious circumstances within the scientific establishment is a recurrent theme in Slotten’s book. The author cites the so-called spiritualist wars of 1870s London, which featured vitriolic exchanges in Nature (a journal Wallace had helped found) between Wallace and such figures as William B. Carpenter, a physiologist, anatomist, and dedicated ghost buster. The occasion was only one of many, Slotten tells us, in which Wallace found himself at loggerheads with colleagues who had revered him as an evolutionist.

By the late 1860s, evolutionary theory itself was no longer safe from Wallace’s unorthodox ponderings, and he began publishing several provisos, much to Darwin’s horror. In a collection of essays that appeared in 1870, Wallace claimed that natural selection was not a strong enough process to have caused the appearance of humans, and he invoked a Supreme Intelligence. In a shockingly vehement reproach, Darwin told his friend: “You write like a metamorphosed (in retrograde direction) naturalist. . . . Eheu! Eheu! Eheu! . . . I defy you to upset your own doctrine.”

The publication of the 1870 essays was the beginning of Wallace’s descent into theism. His flirtations with such unpopular causes as spontaneous generation, antivaccinationism, and land nationalization, combined with his newfound belief in God, made him a highly controversial figure. And yet, several times when his popularity appeared to hit rock bottom, he rekindled it with such masterpieces of natural history as The Geographical Distribution of Animals (1876) and Island Life (1880). The latter, in fact, spurred Darwin and Huxley to arrange a civil pension for the often penurious Wallace.

Slotten seems as bewildered as Wallace’s Victorian contemporaries were by his eclecticism, and makes little attempt to explain Wallace’s many-sided personality. He calls Wallace “a paradox to everyone but himself,” and documents his intellectual twists and turns with a hint of pity.

Historian Martin Fichman has a different take on Wallace. In An Elusive Victorian, he condemns the caricature painted by those who glorify the naturalist-evolutionist Wallace but view the older Wallace as a bit of a crackpot. Instead, Fichman says, “the whole of Wallace’s oeuvre [must be] taken seriously.”

In spite of that admonition, Fichman’s book is not a conventional, chronological biography. He says little about Wallace’s personal life, and the obvious comparison with Darwin, a main theme of other biographies (including Slotten’s), is largely absent. Instead, Fichman takes a thematic approach, analyzing each of Wallace’s main preoccupations in turn. A disadvantage of the method is that the text becomes a bit repetitive here and there, with, for instance, identical (and sometimes quite long) excerpts from Wallace’s writings quoted in multiple chapters. For the rest, the writing is elegant and accomplished (though, to my taste, too cluttered with jargon from the humanities).

Fichman’s main point is that Wallace himself sought to integrate all his various interests and convictions into a single view of life. Wallace the spiritualist believed that what he saw at séances was real proof of a higher level of human existence; he thought spirits could form societies infused with a benevolence that most flesh-and-blood humans had not yet achieved. But Wallace the socialist was confident that such benevolent societies would eventually come into existence. Thus, humans had already evolved to rise above the mere material stage at which other organisms were still stagnating.

And Wallace the evolutionist, according to Fichman, felt that the human spirit—even the mind, the faculty of speech, and the “marvelous beauty and symmetry of his whole external form”—had attained a level far beyond that needed for mere survival and reproduction, and that, therefore, human evolution was no longer within the realm of natural selection. In The World of Life: A Manifestation of Creative Power, Directive Mind, and Ultimate Purpose, published three years before his death in 1913, Wallace the teleological theist invokes God as the great instigator and director of life, and places the world at the center of the universe to act as the stage for the evolution of man, the crowning glory of creation.

It is a surprising conclusion for the man who is often mentioned in the same breath as Darwin, and Fichman does a good job of trying to explain how Wallace the evolutionist arrived at such a mystical, utopian optimism. From Fichman’s fascinating re-creation and analysis of the intellectual world Wallace moved in, it is clear that many beliefs that are held in disrepute today were hardly unique to Wallace. Lyell believed in special creation for humans; William Crookes, the inventor of the cathode-ray tube and the discoverer of thallium, was a spiritualist, as was the statistician Francis Galton, one of Darwin’s cousins.

Yet I am not entirely convinced that Wallace’s “evolutionary teleological theism” is as diligently constructed a theory as Fichman claims it to be. Wallace’s posture as a defender of spiritualism, in the face of repeated exposures of fraudulent practices, is that of a believer, not of an objective scientist. Perhaps that is not surprising, considering the role of spiritualism in Wallace’s personal life. He credited mediums with bringing him into contact with three dead siblings, including his younger brother, Edward, who had died of yellow fever while assisting Wallace in the Amazon.

Wallace also seems to have reveled in debate, and he often started an argument just for the fun of it. Slotten describes how he casually picked a fight with Darwin over the latter’s theory of sexual selection, which Wallace did not accept. Darwin was pained by their disagreement, and he wrote to Wallace to say so. But Wallace seemed to have lost no sleep over the skirmish, and replied to Darwin lightheartedly: “Pray don’t distress yourself. . . . It will all come right in the end.” Wallace once told a friend, “An uphill fight in an unpopular cause . . . has charms for [me] that [I cannot] resist.”

Perhaps the greatest accomplishment of the two new books is to show that there was no “other Wallace.” Through the rich sources that inform them, the reader is afforded penetrating glimpses into Wallace’s many idiosyncrasies. He emerges as a kind, somewhat naive and gullible man, quietly suffering personal pains—but also as a man of keen intellect. After reading almost a thousand pages of Wallaceana by Slotten and Fichman, I am left with the impression of a sometimes brilliant mind struggling, perhaps not completely successfully, to reconcile the good choices with the bad and forge them into a single life. And what a life it was!

Menno Schilthuizen is an associate professor of evolutionary biology at the University of Malaysia Sabah. He is the author of Frogs, Flies, and Dandelions: The Making of Species (Oxford University Press, 2001).

By Laurence A. Marschall

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The Big One: The Earthquake that Rocked Early America and Helped Create a Science by Jake Page and Charles Officer, Houghton Mifflin, 2004; $24.00

W hich of the lower forty-eight states has survived the most powerful earthquake ever recorded in the United States? Strange to relate, the answer is not California, but Missouri. In the middle of the night, on December 16, 1811, the residents of the town of New Madrid awoke to a churning in their stomachs and a rumbling in their ears. Stumbling into the darkness, they saw the ground flapping like a wind-tossed sheet, buildings crumbling all around, and, some claimed, the Mississippi reversing itself, flowing toward the north.

Radiating tremors tumbled homesteaders from their beds in neighboring Kentucky and shook church bells in Charleston, South Carolina. Aftershocks continued for months, and two more major temblors shook the Earth again on January 23 and February 7, 1812, finishing off what the December quake had not destroyed and rattling windows in Montreal, a thousand miles away. By the time the entire episode was over, the course of the Mississippi had been changed in many places, and a new landscape of lakes and ridges had been sculpted. Entire towns had disappeared.

At the beginning of the nineteenth century all this was a puzzlement; when and where earthquakes might occur was anybody’s guess. According to Jake Page, a science writer, and Charles Officer, a geologist, the scientists of the day had only the faintest idea that earthquakes might be associated with volcanoes or tectonic forces. They had no way of making quantitative records of geologic disturbances, and they knew nothing of the Earth’s interior. To those who relied on guesswork and quasi-scientific analogy, earthquakes were traceable to such factors as unfavorable wind conditions, electrical disturbances, and the natural wrinkling of the Earth’s cooling crust. To the pious, earthquakes were acts of divine retribution—though why Missouri deserved God’s wrath any more than Washington, D.C., or New York City was, then as now, a theological enigma.

Page and Officer take the New Madrid quake as a point of departure for their genial history of modern earthquake science. Seismographs were a key development: a host of clever recording devices were introduced by British, Japanese, and Italian inventors in the mid 1800s. The infant science of seismology made it possible to listen to the “sound” of Earth’s interior in response to temblors, just as you can tell whether a tree is hollow by the sound it makes when you tap on its trunk. In time, seismograph recordings enabled geologists to determine that Earth has a dense core surrounded by a slowly flowing mantle and a thin outer crust.

Seismology also led to the mapping of earthquakes all over the planet, and thus to the realization that some regions—the edges of the Pacific Ocean, for instance—are more prone to quakes than others. By the middle of the twentieth century such earthquake-prone zones were recognized as the intersections of tectonic plates, huge rafts of crustal material that float on the mantle and jostle each other ponderously, like giant floes in packs of sea ice. Most earthquakes came to be understood as a natural consequence of the sticking and sudden slippage of crustal plates in contact with each other, the fitful adjustments of continents in motion.

The New Madrid earthquakes, however, remained strange and puzzling, because they were centered far from the margins of tectonic plates: half a continent away from the San Andreas fault to the west, half a continent and half an ocean away from the Mid-Atlantic Ridge to the east. Page and Officer explain how investigators working in the New Madrid area during the past decade have located a fault, known as the Reelfoot Rift, inside the crust, buried several kilometers deep beneath the sediment of an ancient inland sea and, overlying that, the deposits of the Mississippi River and its tributaries. It was the sides of this deep crack that slipped in 1811. Aftershocks continued for several years, and small earthquakes still waggle seismographs in the region.

So when, exactly, is the next “big one” due to hit the nation’s midsection? On this point Page and Officer judiciously demur. In spite of two centuries’ worth of increasing seismic savvy, earthquake prediction remains almost as much a magic art as it was in 1811. Still, if I were planning a move to Missouri, I wouldn’t buy a penthouse condo, no way, no matter how attractive the price.

Sunken Cities, Sacred Cenotes, and Golden Sharks: Travels of a Water-Bound Adventurer by Bill Belleville, University of Georgia Press, 2004; $29.95

Just about the time that you, dear reader, are pulling out of your driveway, heading for your daily aggression-filled hour on the expressway or inbound commuter train, Bill Belleville is probably tumbling backward off the gunwale of a diving boat into a crystal-blue ocean. An environmental journalist and filmmaker, Belleville has managed to make a decent living, as far as one can figure from these enjoyable essays, out of visiting ecologically engaging underwater sites in the West Indies and in Central and South America, and then writing about it for the folks at home. Nice work if you can get it.

It’s not all dog-paddling in a heated pool, though. Belleville is an expert diver whose wanderlust takes him to places few sane people would venture. In one early scene in the book he is dangling in a harness fifty feet above the water level of an overgrown limestone cenote, or sinkhole, deep in the jungle of the Dominican Republic. From that precarious position, a winch will lower him down to an inflatable raft floating on the shadowed waters far below. With a team of scuba-clad archaeologists, he will dive more than a hundred feet farther down into the cenote, to a pinnacle of rock that rises from the pit’s bottom (some 250 feet under water). From there, he and the rest of the team will get their bearings as they search for artifacts tossed into the sinkhole by pre-Columbian tribes as a sacrifice to their gods.

It’s cold, dark, and claustrophobic down there, with practically no margin for carelessness. But the journey, which leads to the discovery of shards of ancient pottery and the bones of extinct sloths, makes for a story of great suspense.

Equally chilling is Belleville’s account of a nocturnal dive off the coast of Cuba in search of the rarely seen, bioluminescent flashlight fish (Kryptophanaron alfredi). To spot its soft radiance, Belleville and a companion turn off their lamps before descending into near total darkness, aiming for an underwater cliff top. They can see neither their depth gauges, the research vessel above them, nor even one another. Except for the increasing crush of water pressure, the luminous flashes of the passing marine life, and the glow of their own ascending air bubbles (which roil the abundant plankton in the water), the effect is one of almost total sensory deprivation.

When Belleville finally pulls up, turns on his light, and looks at his digital wrist gauge, he finds that he’s dropped almost 110 feet, probably overshooting the target. For a tense ten minutes Belleville wanders around alone searching for his partner, whose light, if it’s on, is nowhere in sight. He’s afraid to swim very far in any one direction, terrified that, should he be forced to surface too far from the boat, he’ll be lost from sight, a helpless dot in the choppy waters that surround Cuba.

Fortunately for Belleville (and for readers with a low tolerance for stress), most of the brief excursions he describes in his book take place in far less threatening, though no less interesting, settings. Short essays describe travels to the interior of central Guyana, where rugged jungle and towering waterfalls become exotic destinations for ecotourism; to the ominously named Mosquito Coast of Nicaragua, where conservationists try to enlist native fishermen in a project to preserve endangered sea turtles; and to the Peruvian Amazon, where a team of biologists is studying the behavior of the boto, an unusual, pink, freshwater dolphin. Belleville’s account of the commercial conch farm he visits on one of the Turks and Caicos Islands, an archipelago southeast of the Bahamas, depicts an operation not unlike that of a Midwest cattle ranch—though the conchs, which look like foot-long garden slugs, are destined for soup pots around the Caribbean, not fast-food joints in Tulsa.

Yet such is Belleville’s talent that even when he ventures into relatively familiar territory, he brings an unfamiliar perspective, finding adventure and wonderment in little-seen corners of the natural world. In one episode he describes cave-diving on the Suwannee River in northern Florida, and rejoices in "the singular wonder of being inside the living veins of the earth." In another, he and a college friend take a canoe trip into the heart of the Everglades. There, only a few dozen miles from the strip malls and beachfront condos where former commuters go to live out their days, are worlds out of time: transparent channels filled with needlefish, lone ospreys gliding past tangled mangrove shores, flocks of sulfur-winged butterflies.

Vanilla: Travels in Search of the Ice Cream Orchid by Tim Ecott, Grove Press, 2004; $22.00

What may be the first American recipe for vanilla ice cream, written in the same hand that penned the Declaration of Independence, is among Thomas Jefferson’s papers at the Library of Congress. The vanilla flavoring Jefferson used in his kitchen, made from the seedpods of a rare tropical orchid, had already been popular in Europe for nearly three centuries. The Aztecs showed the Spaniards how vanilla could sweeten their chocolate and perfume their cigars, and the long, dark vanilla beans became part of the Spanish empire’s rich colonial trade as early as the middle of the sixteenth century.

Privateers from European nations were soon looking for the stuff during their raids of Spanish galleons, and their booty was directly responsible for Queen Elizabeth I’s passion for vanilla-flavored desserts. By the end of the seventeenth century such influential Englishmen as Samuel Pepys and Christopher Wren were frequenting coffeehouses where cocoa drinks, flavored with vanilla, were popular menu items. Starbucks, Häagen-Dazs, and the myriad of other food and drink purveyors that rely on vanilla today are thus the beneficiaries of a venerable and pleasant addiction.

The vanilla bean has been prized throughout its long history, not only for its flavor, but also for its great scarcity. Even today only about 2,200 metric tons of beans reach the world’s agricultural markets each year, and the going price for the good stuff in 2004 was close to $275 a pound. Such precious commodities breed violence, and Tim Ecott, whose book recounts his travels to the principal growing sites of the vanilla orchid, needed the steel nerves of a war correspondent to cover this story.

Buyers for the major companies that trade in vanilla travel to remote jungle locations in Indonesia, Madagascar, Mexico, and Papua New Guinea, chartering private planes under aliases to confuse competitors. They carry suitcases stuffed with millions of dollars in cash and visit wealthy growers whose warehouses are surrounded by razor wire and armed guards. Stories of extortion, fraud, and murder in the vanilla trade are as brutal as those told of diamond dealers or heroin smugglers.

The vanilla orchid, its essence so easy on the tongue, has not made things easy for the grower. Although its vine flourishes in many tropical climates, the plant produces no seedpods unless it is fertilized. In nature, that work is done—but only rarely—by a species of tropical bee native to Mexico and Central America. The bee preserved the Spanish domination of the vanilla trade for many centuries. Early vanilla-lovers from other countries, hoping to break the monopoly, managed to transplant cuttings to other parts of the globe, but it was not until the middle of the 1800s that a slave named Edmond, on the French colony of Réunion in the Indian Ocean, devised a way to manually inseminate the plants.

Edmond’s discovery laid the groundwork for the global trade Ecott writes about, but producing vanilla remains a tedious and time consuming process. It takes months for the seedpods to develop, and months more to cure the seeds. Once the vanilla beans reach the processing factory, extracting the concentrated flavoring can take weeks more, because the dried beans must be steeped in alcohol. Ecott’s fascinating travelogue makes it clear that the high price of that little vial of natural vanilla extract is, by any measure, a bargain.

Modern chemists have learned to synthesize the principal ingredient of vanilla, and more than 90 percent of vanilla-flavored foods now contain the artificial stuff. But the real beans contain an estimated 400 trace components that greatly enhance the flavor, and natural vanilla will surely reign supreme for a long time among lovers of good food.

Laurence A. Marschall, author of The Supernova Story, is the W.K.T. Sahm professor of physics at Gettysburg College in Pennsylvania, and director of Project CLEA, which produces widely used simulation software for education in astronomy.

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Slip-Sliding Away By Robert Anderson

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I’m predicting a landslide in November, but not the political kind. I’m talking about the sudden shift of hundreds or thousands of tons of rock and soil, and that kind happens nearly every day. To catch up on the latest tolls in death and destruction from major landslide events, go to the U. S. Geological Survey’s (USGS) main site on the subject (landslides.usgs.gov), and click on “Recent Landslide Events.”

In some places, such as the San Francisco Bay area, weather and geology seem to conspire with gravity to bring down mountainsides on a regular basis. You can get the details from a section of the USGS Web site dedicated to the causes and effects of El Niño (walrus.wr.usgs.gov/elnino/). Scroll down the page to the “Landslides” section, click on “Potential San Francisco Bay Landslides,” then click on “fly-by movies.” Download a cross-sectional view of a “slow-moving failure” and watch it undermine a typical California hillside home, or take a virtual flight over Marin County or East Bay Hills to get some idea of how prevalent landslides have always been in the region. Beneath the fly-by features, you’ll find movies of two actual slides from the 1996–97 rainy season.

Many things can set critically unstable rock in motion. On May 18, 1980, about a mile below Mount Saint Helens, a magnitude 5.1 temblor triggered the largest landslide worldwide in the past century (see pubs.usgs.gov/publications/msh/climactic.html and click on “Debris avalanche”). The mountain shed 0.7 cubic miles of rock, uncorking the more infamous eruption.

Human activities sometimes set the stage for catastrophic landslides. Logging is a good example. Steep slopes denuded of trees and cut with new roads don’t stay put for long. The Sierra Legal Defence Fund has issued a report on the problem in British Columbia, titled “Going Downhill Fast” (www.sierralegal.org/reports/landslide_toc.html). The deadliest and most infamous landslide in Canadian history, the Frank Slide of 1903 in southwestern Alberta, may have been triggered instead by badly regulated coal mining beneath the unstable crest of Turtle Mountain. The resultant landslide brought some 90 million tons of rock down on the sleeping town of Frank, and claimed at least seventy lives (see www.canadiangeographic.ca/Magazine/ma03/alacarte.asp and “The Day the Mountain Fell,” at www3.sympatico.ca/goweezer/canada/frank.htm).

The greatest potential for disaster, however, may lie offshore. Enormous blocks of volcanic islands or continental shelf can give way and travel miles underwater. As the landslide material comes to rest on the deep-sea floor, the sudden displacement of a huge vertical column of seawater can kick up deadly tsunamis across wide areas. The Monterey Bay Aquarium Research Institute provides a good explanation of how such submarine landslides have shaped the Hawaiian Islands (www.mbari.org/volcanism/Hawaii/HR-Landslides.htm). To find out more about submarine landslides, visit the site of New Zea-land’s National Institute of Water and Atmospheric Research (www.niwa.co.nz/pubs/wa/09-1/avalanche.htm).

Earth, of course, is not the only planet where geologic processes combine to tear down and level the sur-face material. At “Geology of Mars” (www.lukew.com/marsgeo/index.html), a Web site created by Albert T. Hsui, a geologist at the University of Illinois at Urbana-Champaign, you’ll learn about the “mass movements” on the Red Planet. Many of them cluster around the huge Valles Marineris, a continent-size canyon that gives gravity some steep cliffs to work with.

Robert Anderson is a freelance science writer living in Los Angeles.

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Copyright © Natural History Magazine, Inc., 2004